The Nature of Plants by Huegel Craig N.;

Author:Huegel, Craig N.; [Неизв.]
Language: eng
Format: epub
Publisher: University Press of Florida
Published: 2019-11-06T20:00:00+00:00

INNER STEM STRUCTURE

In most ways, the inner structure of a stem resembles that of a root. The major differences lie mostly in the way the three tissue systems are designed. Stems of all vascular plants have dermal, vascular, and ground tissue.

The dermal layer of herbaceous stems and the periderm of woody ones have only minor differences from the dermal layer of roots. Although the cell types are virtually identical, the root dermal layer produces trichomes (root hairs), whereas the stem may not. When present, stem trichomes take a completely different form, and they can assume a great many shapes. None is involved in absorbing water. The dermal layer in many herbaceous species also produces a waxy cuticle on the surface of the stem to impede water loss. Such a function is incomprehensible for a root. Roots are designed to maximize water absorption, not impede it.

Stems transport water from the roots to the top of the plant and transport other materials, such as sugars and hormones, in both directions between the foliage and the roots. These materials are carried within the xylem and phloem, respectively. The cells of the vascular tissue in a stem are identical in structure to those of a root. The cells are arranged a bit differently in a stem, but that does not affect the way they work.

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